The spatial focus of attention is controlled at perceptual and cognitive levels.

Selective attention has been hypothesized to reduce distractor interference at both perceptual and postperceptual levels (Lavie, 2005), respectively, by focusing perceptual resources on the attended location and by blocking at postperceptual levels distractors that survive perceptual selection. This study measured the impact of load on these selection mechanisms using a flanker paradigm (Eriksen & St. James, 1986) and indexing distractor interference as a function of separation. It distinguished changes in the extent of focus of the distractor-interference function of separation (reflecting perceptual selection) from changes in the amplitude of distractor interference not accompanied by changes in focus (reflecting postperceptual selection). It showed that: (1) the spatial profile of perceptual resources is shaped like a “Mexican hat” (Müller et al., 2005); (2) increasing perceptual load focuses perceptual resources (Caparos & Linnell, 2009); (3) increasing cognitive load defocuses perceptual resources; and (4) participants with reduced working-memory span show reduced postperceptual blocking of distractors. While these findings are consistent with two levels of selective attention, they show that the first perceptual level is affected not only by perceptual but also by cognitive-control mechanisms. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Dilution: A theoretical burden or just load? A reply to Tsal and Benoni (2010).

Load theory of attention proposes that distractor processing is reduced in tasks with high perceptual load that exhaust attentional capacity within task-relevant processing. In contrast, tasks of low perceptual load leave spare capacity that spills over, resulting in the perception of task-irrelevant, potentially distracting stimuli. Tsal and Benoni (2010) find that distractor response competition effects can be reduced under conditions with a high search set size but low perceptual load (due to a singleton color target). They claim that the usual effect of search set size on distractor processing is not due to attentional load but instead attribute this to lower level visual interference. Here, we propose an account for their findings within load theory. We argue that in tasks of low perceptual load but high set size, an irrelevant distractor competes with the search nontargets for remaining capacity. Thus, distractor processing is reduced under conditions in which the search nontargets receive the spillover of capacity instead of the irrelevant distractor. We report a new experiment testing this prediction. Our new results demonstrate that, when peripheral distractor processing is reduced, it is the search nontargets nearest to the target that are perceived instead. Our findings provide new evidence for the spare capacity spillover hypothesis made by load theory and rule out accounts in terms of lower level visual interference (or mere “dilution”) for cases of reduced distractor processing under low load in displays of high set size. We also discuss additional evidence that discounts the viability of Tsal and Benoni's dilution account as an alternative to perceptual load. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Concurrent working memory load can facilitate selective attention: Evidence for specialized load.

Load theory predicts that concurrent working memory load impairs selective attention and increases distractor interference (N. Lavie, A. Hirst, J. W. de Fockert, & E. Viding, see record 2004-17825-003). Here, the authors present new evidence that the type of concurrent working memory load determines whether load impairs selective attention or not. Working memory load was paired with a same/different matching task that required focusing on targets while ignoring distractors. When working memory items shared the same limited-capacity processing mechanisms with targets in the matching task, distractor interference increased. However, when working memory items shared processing with distractors in the matching task, distractor interference decreased, facilitating target selection. A specialized load account is proposed to describe the dissociable effects of working memory load on selective processing depending on whether the load overlaps with targets or with distractors. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Load induced blindness.

Although the perceptual load theory of attention has stimulated a great deal of research, evidence for the role of perceptual load in determining perception has typically relied on indirect measures that infer perception from distractor effects on reaction times or neural activity (see N. Lavie, 2005, for a review). Here we varied the level of perceptual load in a letter-search task and assessed its effect on the conscious perception of a search-irrelevant shape stimulus appearing in the periphery, using a direct measure of awareness (present/absent reports). Detection sensitivity (d′) was consistently reduced with high, compared to low, perceptual load but was unaffected by the level of working memory load. Because alternative accounts in terms of expectation, memory, response bias, and goal-neglect due to the more strenuous high load task were ruled out, these experiments clearly demonstrate that high perceptual load determines conscious perception, impairing the ability to merely detect the presence of a stimulus--a phenomenon of load induced blindness. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

No negative priming without cognitive control.

There is evidence that the efficiency of selective attention depends on the availability of cognitive control mechanisms as distractor processing has been found to increase with high load on working memory or dual task coordination (Lavie, Hirst, de Fockert, & Viding, 2004). We tested the prediction that cognitive control load would also affect the negative priming effect produced when a distractor from 1 trial appears as a target on the next trial. We measured priming on trials that involved either high or low cognitive control load, and found that under high control load, negative priming was eliminated, and could even be reversed to positive priming, suggesting that the negative priming effect depends on the availability of cognitive control resources. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Diluting the burden of load: Perceptual load effects are simply dilution effects.

The substantial distractor interference obtained for small displays when the target appears alone is reduced in large displays when the target is embedded among neutral letters. This finding has been interpreted as reflecting low-load and high-load processing, respectively, thereby supporting the theory of perceptual load (Lavie & Tsal, 1994). However, a possible alternative interpretation of this effect is that the distractor is similarly processed in both displays, yet its interference in the large ones is diluted by the presence of the neutral letters. We separated the effects of load and dilution by introducing dilution displays. They contained as many letters as the high-load displays but were clearly distinguished from the target, thus allowing for a low-load processing mode. Distractor interference obtained under both the low-load and high-load conditions disappeared under the dilution condition. Hence, the display size effect traditionally misattributed to perceptual load is fully accounted for by dilution. Furthermore, when dilution is controlled for, it is high load not low load producing greater interference. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The effect of perceptual load on attention-induced motion blindness: The efficiency of selective inhibition.

Recent visual marking studies have shown that the carry-over of distractor inhibition can impair the ability of singletons to capture attention if the singleton and distractors share features. The current study extends this finding to first-order motion targets and distractors, clearly separated in time by a visual cue (the letter X). Target motion discrimination was significantly impaired, a result attributed to the carry-over of distractor inhibition. Increasing the difficulty of cue detection increased the motion target impairment, as distractor inhibition is thought to increase under demanding (high load) conditions in order to maximize selection efficiency. The apparent conflict with studies reporting reduced distractor inhibition under high load conditions was resolved by distinguishing between the effects of "cognitive" and "perceptual" load. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Perceptual load influences selective attention across development.

Research suggests that visual selective attention develops across childhood. However, there is relatively little understanding of the neurological changes that accompany this development, particularly in the context of adult theories of selective attention, such as N. Lavie's (1995) perceptual load theory of attention. This study examined visual selective attention across development from 7 years of age to adulthood. Specifically, the author examined if changes in processing as a function of selective attention are similarly influenced by perceptual load across development. Participants were asked to complete a task at either low or high perceptual load while processing of an unattended probe stimulus was examined using event related potentials. Similar to adults, children and teens showed reduced processing of the unattended stimulus as perceptual load increased at the P1 visual component. However, although there were no qualitative differences in changes in processing, there were quantitative differences, with shorter P1 latencies in teens and adults compared with children, suggesting increases in the speed of processing across development. In addition, younger children did not need as high a perceptual load to achieve the same difference in performance between low and high perceptual load as adults. Thus, this study demonstrates that although there are developmental changes in visual selective attention, the mechanisms by which visual selective attention is achieved in children may share similarities with adults. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

The influence of temporal selection on spatial selection and distractor interference: An attentional blink study.

Both spatial and temporal selection require focused attention. The authors examine how temporal attention affects spatial selection. In a dual-task rapid serial visual presentation paradigm, temporal selection of a target (T1) impairs processing of a second target (T2) that follows T1 within 500 ms. This process is the attentional blink (AB). To test the effects of withdrawing temporal attention, the authors measured concurrent distractor interference on T2 when the distractors were presented during and outside of the AB. Perceptual interference was manipulated by the similarity in color between T2 and concurrent distractors, and response interference was manipulated by the flanker congruency task. Results showed that perceptual interference was larger during the AB. Response interference also increased during the AB, but only when perceptual interference was high. The authors conclude that temporal selection and spatial selection rely on a common attentional process. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of cross-modal and intramodal division of attention on perceptual implicit memory.

Extant results motivate 3 hypotheses on the role of attention in perceptual implicit memory. The first proposes that only intramodal manipulations of attention reduce perceptual priming. The second attributes reduced priming to the effects of distractor selection operating in a central bottleneck process. The third proposes that manipulations of attention only affect priming via disrupted stimulus identification. In Experiment 1, a standard cross-modal manipulation did not disrupt priming in perceptual identification. However, when study words and distractors were presented synchronously, cross-modal and intramodal distraction reduced priming. Increasing response frequency in the distractor task produced effects of attention regardless of target-distractor synchrony. These effects generalized to a different category of distractors arguing against domain-specific interference. The results support the distractor-selection hypothesis. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Top-down control over biased competition during covert spatial orienting.

Larger benefits of spatial attention are observed when distractor interference is prevalent, supporting the view that spatial selection facilitates visual processing by suppressing distractor interference. The present work shows that cuing effects with identical visual displays can grow substantially as the probability of distractor interference increases. The probability of interference had no impact on spatial cuing effects in the absence of distractors, suggesting that the enlarged cuing effects were not caused by changes in signal enhancement or in the spatial distribution of attention. These findings suggest that attentional control settings determine more than where spatial attention is directed; top-down settings also influence how attention affects visual processing, with increased levels of distractor exclusion when distractor interference is likely. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Perceptual and cognitive load interact to control the spatial focus of attention.

Caparos and Linnell (2009, 2010) used a variable-separation flanker paradigm to show that (a) when cognitive load is low, increasing perceptual load causes spatial attention to focus and (b) when perceptual load is high, decreasing cognitive load causes spatial attention to focus. Here, we tested whether the effects of perceptual and cognitive load on spatial focus remain when, respectively, cognitive load is high and perceptual load is low. We found that decreasing cognitive load only causes spatial attention to focus when perceptual load is high and the stimulus encourages this. Moreover, and contrary to the widely held assumption that perceptual load focuses attention automatically (Lavie, Hirst, de Fockert, & Viding, 2004), perceptual load exerts its focusing effect only with the engagement of cognitive resources when cognitive load is low. In sum, perceptual and cognitive mechanisms exert interacting effects and operate in concert to focus spatial attention. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Dilution, not load, affects distractor processing.

Lavie and Tsal (1994) proposed that spare attentional capacity is allocated involuntarily to the processing of irrelevant stimuli, thereby enabling interference. Under this view, when task demands increase, spare capacity should decrease and distractor interference should decrease. In support, Lavie and Cox (1997) found that increasing perceptual load by increasing search set size decreased interference from an irrelevant distractor. In three experiments, we manipulated the cue set size (number of cued locations) independently of the display set size (number of letters presented). Increasing the display set size reduced distractor interference regardless of whether the additional letters were relevant to the task. In contrast, increasing the cue set size increased distractor interference. Both findings are inconsistent with the load explanation, but are consistent with a proposed two-stage dilution account. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Development of selective attention: Perceptual load influences early versus late attentional selection in children and adults.

The moderating effect of perceptual load on visual selective attention was examined in 2 studies. In Study 1, children and young adults searched displays of varying set size flanked by irrelevant distractors. Children's performance was as efficient as adults' under conditions of high but not low loads, suggesting that early selection engages rapidly maturing neural systems and late selection engages later-maturing systems. In Study 2, 4 age groups were tested, and place markers were set at empty locations to examine perceptual grouping effects. Study 1's pattern was replicated in all age groups, with onset of early selection occurring at lower loads for younger children. Overall, children initiated early selection at lower loads to compensate for immature anterior-system interference control processes. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Failures to ignore entirely irrelevant distractors: The role of load.

In daily life (e.g., in the work environment) people are often distracted by stimuli that are clearly irrelevant to the current task and should be ignored. In contrast, much applied distraction research has focused on task interruptions by information that requires a response and therefore cannot be ignored. Moreover, the most commonly used laboratory measures of distractibility (e.g., in the response-competition and attentional-capture paradigms), typically involve distractors that are task relevant (e.g., through response associations or location). A series of experiments assessed interference effects from stimuli that are entirely unrelated to the current task, comparing the effects of perceptual load on task-irrelevant and task-relevant (response competing) distractors. The results showed that an entirely irrelevant distractor can interfere with task performance to the same extent as a response-competing distractor and that, as with other types of distractors, the interfering effects of the irrelevant distractors can be eliminated with high perceptual load in the relevant task. These findings establish a new laboratory measure of a form of distractibility common to everyday life and highlight load as an important determinant of such distractibility. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Working-memory-triggered dynamic adjustments in cognitive control.

Dynamic adjustments in cognitive control are well documented in conflict tasks, wherein competition from irrelevant stimulus attributes intensifies selection demands and leads to subsequent performance benefits. The current study investigated whether mnemonic demands, in a working memory (WM) task, can drive similar online control modifications. Demand levels (high vs. low) of WM maintenance (memory load of 2 items vs. 1 item) and delay-spanning distractor interference (confusable vs. not confusable with memoranda) were manipulated using a factorial design during a WM delayed-recognition task. Performance was best subsequent to trials in which both maintenance and distractor interference demands were high, followed by trials with high demand in either of these 2 control domains, and worst following trials with low demand in both domains. These results suggest that dynamic adjustments in cognitive control are not triggered exclusively by conflict-specific contexts but are also triggered by WM demands, revealing a putative mechanism by which this system configures itself for successful task performance. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Perceptual load as a necessary condition for selective attention.

The early and late selection debate may be resolved if perceptual load of relevant information determines the selective processing of irrelevant information. This hypothesis was tested in 3 studies; all used a variation of the response competition paradigm to measure irrelevant processing when load in the relevant processing was varied. Perceptual load was manipulated by relevant display set size or by different processing requirements for identical displays. These included the requirement to process conjunctions versus isolated features and the requirement to perform simple detection of a character's presence versus difficult identification of its size and position. Distractors' interference was found only under low-load conditions. Because the distractor was usually clearly distinct from the target, it is concluded that physical separation is not a sufficient condition for selective perception; overloading perception is also required. This allows a compromise between early and late selection views and resolves apparent discrepancies in previous work. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Age-related changes in selective attention and perceptual load during visual search.

Three visual search experiments were conducted to test the hypothesis that age differences in selective attention vary as a function of perceptual load (E. A. Maylor & N. Lavie, 1998). Under resource-limited conditions (Experiments 1 and 2), the distraction from irrelevant display items generally decreased as display size (perceptual load) increased. This perceptual load effect was similar for younger and older adults, contrary to the findings of Maylor and Lavie. Distraction at low perceptual loads appeared to reflect both general and specific inhibitory mechanisms. Under more data-limited conditions (Experiment 3), an age-related decline in selective attention was evident, but the age difference was not attributable to capacity limitations as predicted by the perceptual load theory. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Does emotion processing require attention? The effects of fear conditioning and perceptual load.

This study examined the impact of perceptual load on the processing of unattended threat-relevant faces. Participants performed a central letter-classification task while ignoring irrelevant face distractors, which appeared above or below the central task. The face distractors were graded for affective salience by means of aversive fear conditioning, with a conditioned angry face (CS+), an unconditioned angry face (CS?), and a neutral control face. The letter-classification task was presented under conditions of both low and high perceptual load. Results showed that fear conditioned (i.e., CS+) angry face distractors interfered with task performance more than CS? angry or neutral face distractors but that this interference was completely eliminated by high perceptual load. These findings demonstrate that aversively conditioned face distractors capture attention only under conditions of low perceptual load. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Emotion-attention interactions in recognition memory for distractor faces.

Effective filtering of distractor information has been shown to be dependent on perceptual load. Given the salience of emotional information and the presence of emotion-attention interactions, we wanted to explore the recognition memory for emotional distractors especially as a function of focused attention and distributed attention by manipulating load and the spatial spread of attention. We performed two experiments to study emotion-attention interactions by measuring recognition memory performance for distractor neutral and emotional faces. Participants performed a color discrimination task (low-load) or letter identification task (high-load) with a letter string display in Experiment 1 and a high-load letter identification task with letters presented in a circular array in Experiment 2. The stimuli were presented against a distractor face background. The recognition memory results show that happy faces were recognized better than sad faces under conditions of less focused or distributed attention. When attention is more spatially focused, sad faces were recognized better than happy faces. The study provides evidence for emotion-attention interactions in which specific emotional information like sad or happy is associated with focused or distributed attention respectively. Distractor processing with emotional information also has implications for theories of attention. (PsycINFO Database Record (c) 2010 APA, all rights reserved)